The pupillary sphincter adjusts the size of the pupil according to the intensity of light.

His pupils dilated in surprise.

She used a pupil dilator to dilate the patient's pupils.

He decided to satisfy her demands.

His house is very big.

Regulating this machine is difficult.

He used the air conditioner remote to regulate the room temperature.

Only one light was shining into the room.

A sphincter plays a role in opening and closing certain parts of the body.

This tree is very hard.